A number of isoindole-type compounds are known in the prior art. Recently, in German Offenlegungsschrift No. 2,165,651 a group of isoindole-1,3-diones was disclosed as herbicides. The general formula for the isoindole-1,3-diones is as follows: ##STR1## wherein R may be an aryl, aralkyl, or benzyl with optional substituents. U.S. Pat. No. 3,958,976 has disclosed compounds of the following formula as useful for selective weed control in certain crops or for total vegetation control. ##STR2## The preparation of 2-phenyl-5,6,8,8A-tetrahydro-1H-imidazo-[5,1-c][1,4]thiazine-1,3(2H)-dione has been reported in J Med Pharm Chem 2 553 (1960) and J Chem Soc, Perkin I, 132 (1973). The synthesis of 3-carbethoxy-4-phenylaminocarbonyl-5,6-dihydrothiazine has been reported in Gazz. Chin. Ital., 92, 1367 (1962). No agricultural utility was disclosed for either of these compounds. It has now been found that placing proper substituents(s) on the benzene ring in this class of compounds significantly enhances their herbicidal activity.